1. Field of the Invention
The invention relates to highly active and stable ruthenium metal carbene complex compounds and their use as catalysts for olefin metathesis reactions.
2. Description of the Related Art
The formation of carbon-carbon bonds via olefin metathesis is of considerable interest and commercial utility, and considerable research efforts have been undertaken to develop olefin metathesis catalysts and systems. Group VIII transition metal catalysts have proven to be particularly useful for catalyzing olefin metathesis reactions, such as ring-opening metathesis polymerization (ROMP), ring-closing metathesis polymerization (RCM), acyclic diene metathesis (ADMET), and cross metathesis reactions. Both classical and well-defined olefin metathesis catalysts based on ruthenium have been shown to exhibit good tolerance to a variety of functional groups, as has been reported by, e.g., Grubbs, R. H. J. M. S.-Pure Appl. Chem. 1994, A31(11), 1829-1833; Aqueous Organometallic Chemistry and Catalysis. Horvath, I. T., Joo, F. Eds; Kluwer Academic Publishers: Boston, 1995; Novak, B. M.; Grubbs, R. H. J. Am. Chem. Soc. 1988, 110, 7542-7543; Novak, B. M.; Grubbs, R. H. J. Am. Chem. Soc. 1988, 110, 960-96; Nguyen, S. T.; Johnson, L. K.; Grubbs, R. H. J. Am. Chem. Soc. 1992, 114, 3974-3975 and Schwab, P.; Grubbs, R. H.; Ziller, J. W. J. Am. Chem. Soc. 1996, 118, 100, each of which is incorporated herein by reference. In particular, as reported by Lynn, D. M.; Kanaoka, S.; Grubbs, R. H. J. Am. Chem. Soc. 1996, 118, 784 and by Mohr, B.; Lynn, D. M.; Grubbs, R. H. Organometallics 1996, 15, 4317-4325, both of which are incorporated herein by reference, the robust nature of the ruthenium-carbon bonds in these complexes has enabled olefin metathesis reactions to be carried out in protic media. However, slow reaction rates and low yields have limited the application of these catalysts for a variety of olefin monomers and reaction conditions.
As an example, there is a need for homogeneous polymerization systems that are living in water and that will polymerize water-soluble monomers. In living polymerization systems, polymerization occurs without chain transfer or chain termination, giving greater control over polydispersity of the resultant polymers. Such polymerization systems are highly desirable as they would allow the controlled synthesis of water-soluble polymers and would enable precise control over the composition of block copolymers for use, for example, in biomedical applications. However, such polymerization systems represent a formidable challenge. For example, the addition of water to traditional living anionic or cationic systems results in rapid termination. The advent of late transition metal catalysts tolerant of numerous polar and protic functionalities has recently enabled living ring-opening metathesis polymerizations (ROMP), free-radical polymerizations, and isocyanide polymerizations in aqueous environments, as reported by Lynn, D. M.; Kanaoka, S.; Grubbs, R. H. J. Am. Chem. Soc. 1996, 118, 784; Manning, D. D.; Strong, L. E.; Hu, X.; Beck, P.; Kiessling, L. L. Tetrahedron, 1997, 53, 11937-11952; Manning, D. D.; Hu, X.; Beck, P.; Kiessling, L. L. J. Am. Chem. Soc. 1997, 119, 3161-3162; Nishikawa, T; Ando, T; Kamigaito, M; Sawamoto, M. Macromolecules 1997, 30, 2244-2248; Deming, T. J.; Novak, B. M. Polym. Prepr. (Am. Chem. Soc., Div. Polym. Chem.) 1991, 32, 455-456; and Deming, T. J.; Novak, B. M. Macromolecules, 1991, 24, 326-328, each of which is incorporated herein by reference. Although these examples represent significant advances toward entirely aqueous systems, the catalysts themselves are insoluble in water and the polymerization reactions basically occur in "wet" organic phases.
Aqueous ring-opening metathesis polymerization of strained, cyclic olefins initiated by Group VIII salts and coordination complexes is well-documented. Although these complexes serve as robust polymerization catalysts in water, the polymerizations are not living and inefficient initiation steps produce erratic results (typically less than 1% of metal centers are converted to catalytically-active species) and results in poor control over polymer molecular weight.
We recently reported the synthesis of well-defined, water soluble ruthenium alkylidenes which serve as excellent initiators for olefin metathesis reactions in water, methanol, and aqueous emulsions. See Mohr, B.; Lynn, D. M.; Grubbs, R. H. Organometallics, 1996, 15, 4317-4325, incorporated herein by reference. Further investigation of these complexes, however, revealed that potential applications could be limited by relatively fast termination reactions. Similar ruthenium alkylidene complexes are disclosed in U.S. Pat. Nos. 5,312,940 and 5,342,909 and U.S. application Ser. Nos. 08/693,789, filed Jul. 31, 1996, now U.S. Pat. No. 5,836,108, and Ser. No. 08/708,057, filed Aug. 30, 1996, now U.S. Pat. No. 5,710,298, each of which is incorporated herein by reference.
For these reasons, there is a need for well-defined olefin metathesis catalysts and systems with improved efficiencies that provide for increased reaction rates, increased product yields, and that allow for metathesis of a wider range of olefins in a broader range of solvents than previously possible.